From: norman@nose.cs.utoronto.ca (Norman Wilson)
Subject: [TUHS] The ^ = | ?
Date: Thu, 23 Jan 2003 22:09:51 -0500 [thread overview]
Message-ID: <pGdcVJPx3rqv.zrrJXl9y@192.168.0.10> (raw)
The earliest UNIX Programmer's Manual to describe shell
pipelines is the Third Edition, February 1973. It gives a
syntax quite different from the modern one:
com1 > com2 > com3 > outfile
meant what we would now write as
com1 | com2 | com3 > outfile
This original syntax was pretty cumbersome; pretty
obviously it was put in as a quick hack (as were many
things in those early days). Because > and < applied
only to the following word, pipelined commands with
arguments had to be quoted:
who > "grep ken" >/tmp/kenlogins
Even worse, the shell had no inherent way to tell whether
the final word was a file or a program; if the last element
in a pipeline was to write to standard output, you had to
say so explicitly:
who > "grep ken" >
On the other hand the syntax was symmetric: you could
also write
"grep ken" < who <
pipe(II) also debuted in the Third Edition.
By the Fourth Edition (November 1973) there had evidently
been more time to think about the syntax; the modern notation
is shown, except that ^ is allowed as a synonym for |. I have
long guessed that was because in those dark days of the
past, some upper-case-only terminals (remember stty lcase?)
offered no way to type | (and perhaps likewise {}`~) but I don't
really know. Dennis?
Norman Wilson
Toronto ON
next reply other threads:[~2003-01-24 3:09 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-01-24 3:09 Norman Wilson [this message]
2003-01-24 5:37 ` Warren Toomey
2003-01-24 7:07 ` Lars Brinkhoff
2003-01-24 10:32 ` Sven Mascheck
2003-01-26 1:40 ` Greg Lehey
-- strict thread matches above, loose matches on Subject: below --
2003-01-25 8:46 Wolfgang Helbig
2003-01-24 2:09 Carl Lowenstein
2003-01-24 0:04 John Holden
2003-01-23 12:25 Lange, David
2003-01-24 0:05 ` M. Warner Losh
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